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Use atomic key generation in all cases

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This commit is contained in:
Matt Johnston 2016-11-19 00:31:21 +08:00
parent 9f674382d5
commit 5d2cb48f46
6 changed files with 57 additions and 52 deletions
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17
dbutil.c
View File

@ -681,4 +681,21 @@ time_t monotonic_now() {
return time(NULL);
}
void fsync_parent_dir(const char* fn) {
#ifdef HAVE_LIBGEN_H
char *fn_dir = m_strdup(fn);
char *dir = dirname(fn_dir);
int dirfd = open(dir, O_RDONLY);
if (dirfd != -1) {
if (fsync(dirfd) != 0) {
TRACE(("fsync of directory %s failed: %s", dir, strerror(errno)))
}
m_close(dirfd);
} else {
TRACE(("error opening directory %s for fsync: %s", dir, strerror(errno)))
}
free(fn_dir);
#endif
}

2
dbutil.h
View File

@ -89,4 +89,6 @@ time_t monotonic_now(void);
char * expand_homedir_path(const char *inpath);
void fsync_parent_dir(const char* fn);
#endif /* DROPBEAR_DBUTIL_H_ */

2
dropbearkey.c
View File

@ -241,7 +241,7 @@ int main(int argc, char ** argv) {
}
fprintf(stderr, "Generating key, this may take a while...\n");
if (signkey_generate(keytype, bits, filename) == DROPBEAR_FAILURE)
if (signkey_generate(keytype, bits, filename, 0) == DROPBEAR_FAILURE)
{
dropbear_exit("Failed to generate key.\n");
}

39
gensignkey.c
View File

@ -76,10 +76,12 @@ static int get_default_bits(enum signkey_type keytype)
}
}
int signkey_generate(enum signkey_type keytype, int bits, const char* filename)
/* if skip_exist is set it will silently return if the key file exists */
int signkey_generate(enum signkey_type keytype, int bits, const char* filename, int skip_exist)
{
sign_key * key = NULL;
buffer *buf = NULL;
char *fn_temp = NULL;
int ret = DROPBEAR_FAILURE;
if (bits == 0)
{
@ -126,10 +128,37 @@ int signkey_generate(enum signkey_type keytype, int bits, const char* filename)
sign_key_free(key);
key = NULL;
buf_setpos(buf, 0);
ret = buf_writefile(buf, filename);
buf_burn(buf);
buf_free(buf);
buf = NULL;
fn_temp = m_malloc(strlen(filename) + 30);
snprintf(fn_temp, strlen(filename)+30, "%s.tmp%d", filename, getpid());
ret = buf_writefile(buf, fn_temp);
if (ret == DROPBEAR_FAILURE) {
goto out;
}
if (link(fn_temp, filename) < 0) {
/* If generating keys on connection (skipexist) it's OK to get EEXIST
- we probably just lost a race with another connection to generate the key */
if (!(skip_exist && errno == EEXIST)) {
dropbear_log(LOG_ERR, "Failed moving key file to %s: %s", filename,
strerror(errno));
/* XXX fallback to non-atomic copy for some filesystems? */
ret = DROPBEAR_FAILURE;
goto out;
}
}
out:
if (buf) {
buf_burn(buf);
buf_free(buf);
}
if (fn_temp) {
unlink(fn_temp);
m_free(fn_temp);
}
return ret;
}

2
gensignkey.h
View File

@ -3,6 +3,6 @@
#include "signkey.h"
int signkey_generate(enum signkey_type type, int bits, const char* filename);
int signkey_generate(enum signkey_type type, int bits, const char* filename, int skip_exist);
#endif

47
svr-kex.c
View File

@ -93,29 +93,9 @@ void recv_msg_kexdh_init() {
#if DROPBEAR_DELAY_HOSTKEY
static void fsync_parent_dir(const char* fn) {
#ifdef HAVE_LIBGEN_H
char *fn_dir = m_strdup(fn);
char *dir = dirname(fn_dir);
int dirfd = open(dir, O_RDONLY);
if (dirfd != -1) {
if (fsync(dirfd) != 0) {
TRACE(("fsync of directory %s failed: %s", dir, strerror(errno)))
}
m_close(dirfd);
} else {
TRACE(("error opening directory %s for fsync: %s", dir, strerror(errno)))
}
free(fn_dir);
#endif
}
static void svr_ensure_hostkey() {
const char* fn = NULL;
char *fn_temp = NULL;
enum signkey_type type = ses.newkeys->algo_hostkey;
void **hostkey = signkey_key_ptr(svr_opts.hostkey, type);
int ret = DROPBEAR_FAILURE;
@ -151,28 +131,10 @@ static void svr_ensure_hostkey() {
return;
}
fn_temp = m_malloc(strlen(fn) + 20);
snprintf(fn_temp, strlen(fn)+20, "%s.tmp%d", fn, getpid());
if (signkey_generate(type, 0, fn_temp) == DROPBEAR_FAILURE) {
if (signkey_generate(type, 0, fn, 1) == DROPBEAR_FAILURE) {
goto out;
}
if (link(fn_temp, fn) < 0) {
/* It's OK to get EEXIST - we probably just lost a race
with another connection to generate the key */
if (errno != EEXIST) {
dropbear_log(LOG_ERR, "Failed moving key file to %s: %s", fn,
strerror(errno));
/* XXX fallback to non-atomic copy for some filesystems? */
goto out;
}
}
/* ensure directory update is flushed to disk, otherwise we can end up
with zero-byte hostkey files if the power goes off */
fsync_parent_dir(fn);
ret = readhostkey(fn, svr_opts.hostkey, &type);
if (ret == DROPBEAR_SUCCESS) {
@ -190,11 +152,6 @@ static void svr_ensure_hostkey() {
}
out:
if (fn_temp) {
unlink(fn_temp);
m_free(fn_temp);
}
if (ret == DROPBEAR_FAILURE)
{
dropbear_exit("Couldn't read or generate hostkey %s", fn);